Field
The present disclosure relates generally to communication systems, and more particularly, to a system that enables use of multiple radio access technologies.
Background
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). LTE is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
Circuit-switched fallback (CSFB) is a feature of LTE wireless networks that enables user equipment (UE) to connect to other networks that use circuit-switching technologies. For example, a UE may use CSFB to use CS-based voice services while otherwise being connected to an LTE network. In another example, a Voice-over-LTE (VOLTE) supported UE may leave an LTE coverage area; in such instances, the VOLTE-supported call may be subject to handover to a 2G/3G network (e.g., a Single Radio Voice Call Continuity (SRVCC) procedure). As both CS-based and packet-switched (PS) based networks like LTE coexist, there is a need to enable the networks to co-exist and for devices to effectively use both networks based on the service desired.